Combining modelling, field data and genetic variation to understandthe post‑reintroduction population genetics of the Marsh Fritillarybutterfly (Euphydryas aurinia)

The Marsh Fritillary butterfy (Euphydryas aurinia) is a Eurasian species which has sufered signifcant reductions in occurrence and abundance over the past century, particularly across the western side of its range, due to agricultural intensifcation
and habitat loss. This loss has been particularly severe in the UK with extensive localised extinctions. Following sympathetic management, reintroduction was undertaken at four Cumbria (northern UK) sites in 2007 with stock from a captive
admixture population descended from Cumbrian and Scottish founders. Annual population monitoring of the reintroductions
was undertaken. Nine years post-reintroduction, the level of population genetic variation was assessed using microsatellites. Variation in historical Cumbrian samples was determined using museum samples and Scottish samples from current
populations were assayed to characterise natural population variation. Half of the Scottish sites also served as indicators
of the alleles present in the founder populations. The genetic contribution of the founder populations allied to population
size data allowed patterns of genetic variation to be modelled. Alleles from Cumbrian and Scottish founders are present in
the reintroduced populations. The four sites have levels of variation akin to natural populations and exhibit diferentiation
as predicted by statistical modelling and comparable with natural populations. This suggests that reintroduction following
captive breeding can produce self-sustaining populations with natural levels of genetic diversity. These populations appear
to be undergoing the same evolutionary dynamics with bottlenecks and drift as natural populations.